A twist in the geometry of rotating black holes: seeking the cause of acausality

TL;DR

This paper explores the counter-rotation of closed timelike curves in rotating black holes, proposing it may be a fundamental feature of such spacetimes rather than an anomaly.

Contribution

It reveals that CTCs in rotating black holes counter-rotate relative to the black hole’s spin, suggesting a potential general principle behind this phenomenon.

Findings

CTCs counter-rotate against black hole spin

Similar counter-rotation observed in other rotating spacetimes

Proposes a possible fundamental reason for counter-rotation in rotating spacetimes

Abstract

We investigate Kerr-Newman black holes in which a rotating charged ring-shaped singularity induces a region which contains closed timelike curves (CTCs). Contrary to popular belief, it turns out that the time orientation of the CTC is opposite to the direction in which the singularity or the ergosphere rotates. In this sense, CTCs "counter-rotate" against the rotating black hole. We have similar results for all spacetimes sufficiently familiar to us in which rotation induces CTCs. This motivates our conjecture that perhaps this counter-rotation is not an accidental oddity particular to Kerr-Newman spacetimes, but instead there may be a general and intuitively comprehensible reason for this.